Propeller pitch control



May ll, 1954 T. B. MARTIN ETAL 2,678,103

` PROPELLER FITCH CONTROL Filed June 27, 1945 l1 Sheets-Sheet l INVENTOR S ATTORNEY/Q T. B. MARTIN ET AL PROPELLER PITCH CONTROL Y May ll,` 1954 11 sheets-shea 2 Filed June 27. 1945 ATTO ww NN,

May 1l, 1954 T. B. MARTIN ET Al.

PROPELLER FITCH CONTROL 11 Sheets-Sheet 5 Filed June 27. 1945 May l1, 1954 T. B.MART|N ET AL 2,578,103

PROPELLER FITCH CONTROL Filed June 27, 1945 1l Sheets-Sheet 4 u I INVENTORS ATTORN EY May ll, 1954 "r. B. MARTIN ET AL PROPELLER FITCH CONTROL 11 Shets-Sheet 5 .filed June 27, 1945 Nw N INVENTOR ATTORNEW;Y

May 11, 1954 T. B. MARTIN ET A1. 2,678,103' PROPELLER PITCH CONTROL Filed June 2v, 1945 v 1.1 sheets-sheet e COrzZra for. Zlnfeakefmy Jzy INVENTORS WW 4 ATTORN Eri May 1l, 1954 T, B. MARTIN ET AL PROPELLER PITCH CONTROL 11 Sheets-Sheet '7 Filed June 27. 1945 INVENToRs y ATTORNEY May 11, 1954 T. B. MARTIN ET AL 2,678,103

PROPELLER FITCH CONTROL Y .filed June 27, V1945 11 Sheets-sheet 8 INV Tons y f3 l @u MM/ f ATToRNEY/z/ May 11, 1954 T. B. MARTIN ET AL PROPELLER FITCH CONTROL 11 Sheets-Sheet 9 Filed June 27. 1945 May l1, 1954 T, B. MAR'nN ETAL PROPELLER FITCH CONTROL 11 sheets-sheet 1o :iled June 27. 1945 2%@ M'romulamdI May 11. 1954 T. B. MARTIN ET AL 2,678,103

PROPELLER FITCH CONTROL .filed June 27, 1945 11 sheets-sheet 11 l "I --zfd j 1 v NToRs .3f fmvNZM/Wffy @Vw/@J Y ATTORNEY/ Patented May 11, 1954 PROPELLER PITCH CONTROL Thomas B. Martin and James R. May,

Dayton,

Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June 27, 1945, Serial No. 601,786

22 Claims. (Cl. TIO-160.21)

This invention relates to variable pitch airplane propellers and aims to provide a system of pitch control whereby governed positive pitch, governed negative pitch and feathering may be obtained.

Further objects and advantages of the present invention Will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figs. 1 through l6 are diagrams showing the system in different conditions of operation.

Figs. 7 and 8, taken together, constitute a longitudinal, sectional view of the propeller hub which includes the pitch control system shown in Fig. 1. The section through the regulator unit 200 is taken on the line 1-1 of Fig. 10.

Fig. 9 is an enlarged, sectional view on line 9 9 of Fig. 7.

Fig. 10 is a sectional view on line Ill-Ill of Fig. 7.

Fig. 11 is a sectional view on line I I|| of Fig. 10.

Fig. 12 is a sectional view on line |2-l2 of Fig. 10.

Fig. 13 is a sectional view on line |3-I3 of Fig. 10.

Fig. 14 is a plan view of the regulator unit base 2|!! shown in section in Fig. 7, the various instruments being omitted with the exception of triple gear pump |60.

Fig. 15 is a sectional view on line |5-I5 of Fig. 14.

Fig. 16 is a sectional view on line Fig. 14.

I6-I6 of Fig. 17 is a sectional View on line Il-I'I of the pump |60 of Fig. 14.

Fig. 18 is a sectional view on line |8-|8 of Fig. 14.

Fig. 19 is a fragmentary, sectional view of that portion of the propeller hub and regulator assembly which shows the control of the feathering valve 9B and the negative pitch control valve |20 and is taken on line I 9| 9 of Fig. 10.

Fig. 20 is an enlarged sectional view of the feathering control valve 99 and is taken on the line Iii-I9 of Fig. 10.

Fig. 2l is a view in the direction of arrow 2| of Fig. 20.

Fig. 22 is a fragmentary view in the direction of arrow 22 of Fig. 20.

Figs. 23 and 24 are fragmentary, sectional views showing portions of the feathering control valve in diiierent positions of operation.

CII

Fig. 25 is a side view of cam follower 2302 shown in Fig. 19.

Fig. 26 is a side view of cam 3| 3 shown in Fig. 19.

Figs. 27 and 28 are perspective views of the parts of a cam unit used for controlling the feathering valve 30 and the negative pitch valve |20.

Fig. 29 is a plan View of one side of the cam assembly comprising the parts shown in Figs. 27 and 28.

Fig. 30 is a plan view of the reverse side of the assembly.

Figs. 31 and 32 are elevational views taken in the direction of arrows 3| and 32 of Fig. 29.

Referring to Fig. 1, the propeller shaft Ill drives a plurality of propeller blades, one of which is shown in section and designated by numeral II. The root of propeller is represented by circle l2 and the axis of root rotation by numeral I3. The torque unit or means for rotating the blade about the axis |3 comprises a cylinder I5 receiving a piston I6 connected with a rod Il proividing a rack I8 meshing with a gear segment I9 connected with the root I2. It is to be understood that the rack and gear segment for transmitting movement from the piston rod to the blade root are symbolic of other forms of mechanisms for transmitting motion from a servopiston to the rotatable blade root known to those skilled in the art. The ends of the cylinder l5 are connected by pipes 2l and. 22 with a switchover valve unit 22 comprising a cylinder 23 containing a valve 24 having grooves 25, 26 and 21 separating lands 28, 29, 30 and 3|. The groove 25 is connected by holes 32 with a central chamber 33 of the valve 24. Holes 34 connect groove 2l with the central chamber 33. A spring 35 urges the Valve 24 toward the left. Pipes 3B and 31 connect the unit 2E! with the governor unit 4B which comprises a sleeve 4| receiving a valve 42 having lands 43 and 44 and connected by a pin 45 with a lever 46 engaging an adjustable fulcrum 4l against which it is urged by a spring 4S. Valve 42 is under joint control by centrifugal force acting in the direction of arrow 42a and by the spring 48 opposing centrifugal force, the effectiveness of spring 48 being determined by the position of the fulcrum 4l which is adjustable horizontally in Fig. 1 from a position near the left end of the lever 46 toward the right. The position of the fulcrum 41 is controlled manually by means to be described later. When the valve 42 is in the equilibrium position causing the torque unit to hold the blade in the Vber into which is forced air under pressure adjusted position, Vthe force couple of the spring i8 relative to the fulcrum 51 equals the force couple of the centrifugal force acting upon the valve 42. Since the governed speed of the engine is controlled manually by shifting the fulcrum lil, the Vgoverned speed of the engine is manually adjusted.

The governor unit i5 is connected by a pipe 45 with a pressure-control valve unit 55 comprising cylinders i, 52 and 53. Cylinder 5| receives a notched dashpot plate 55 carried by rod 55 surrounded by a spring 55 which urges the rod 55 upwardly. The rod 55 a piston valve 5l slidable in cylinder 52 having a vent 52a. Valve 5l' controls ports 55 and v55. The lower end of rod 55 provides the piston in cylinder 55. The cylinder 53 is connected by pipe 55 with pipe 36. The cylinder 5i is connected by pipe 5| with a feathering valve ,95 and.

with a pipe 85. Rod 55 and parts movable therewith are under the action of centrifugal force-acting in the direction of arrow 55 t..

The ports 58 and 55 are connected by a pipe Y 52 with a pump-control valve unit l5' `comprising a cylinder H enclosing a valve l2 havingY grooves 'iSv'and 'le which separate lands '55, l5 and 'il'. Thecylinder 'il has outlets l2 and l5. The groove 'l5 is connected with the space above the land ll by the small internal passages ica.. In response to the action oi Acentrifugaliorcavalve 'i2 tendsl to move upwardly as indicated by arrow 12a.

Cylinder 'il is connected by pipes S5 vand 5| with an outlet of an auxiliary Vhigh capacity pump. 52. having an inlet B3. Valve cylinder li is connected by Ypipe 85,' check valve 55. and

pipe 35 with a pipe 85 connecting the outlet of The shoulder 5l at the junction of the ycyl-` inders 52 and 93 provides a valve seatcooperating with a conical valve 58 vprovided by the valve 55. Between the land 95 and the valve 53 there is a groove 95 connected by a cross passage 55V anda longitudinal passage lili with a recess 552 which receives a spring' 53 urging a check valve ball |54 against a seat |55V thereby ynormally closing a longitudinal passage |55 whichv is connected by cross passages lill with the spacebetween the land gli andthe conical valve 58. A spring V|55 urges the valve 95 toward the left. The cylinder 53 is vented at |59.V Valve |55 is controlled by a rod H5 passing through a seal iia and engageable with Van adjustable screw threaded into a llever H2 pivotally'supported at |23 by the valve body 'Si and urged'counterclockwise against a stop l! by a spring l5; W'hen Vlever H2 is in the position shown in Fig. l, valve |835 Vis seated by spring-|53.Y Lever H2 carries aLlug H6 engageable-with a lug Il? attached to a bar ||8 movable horizontally and vproviding a support Hilft for the iulcrum lil. Body 9i is connected by a-pipe ||9c with an accumulator H9 having a diaphragm H91;V separating the upper, hydraulic-fluid receiving space from an air chamand retained by a check valve l| |95. Y

The pitch control unit |25 comprises a body i2| having a cylinder |22 for receiving a valve l'having lands |25 and |25 separated by groove V|26V and'urgedto the right by spring |27 4 which causes the valve |23 always toV engage a cam |35 which is operatively connected with the blade roots I2. The cam |35 has a land iti for positive governed pitch control, a land 52 for the change between the positive and negative governed pitch control and a land |33 for negative governed pitch control. The valve body |2| has a cylinder |40 having outlets lill, |52, and |53. Valve cylinders |22 and |51) are connected by ports |44 and |45. Cylinder |55 receives a valve |43 having lands |57, |55', |55 and |513. Valve |56 is urged left by a spring so that Vit may engage a cam bar |5| having a low land |52 and a high land |53. An arrow |54 on the vbar I5! points to line P and indicates .when the bar |5| is in the positive pitch control `position in which the low land |52 is-engaged by the Valve |55. When, by manual means similar to that used for adjusting the fulcrum il of governor unit 4i), the bar |5i is moved upwardly in Fig. 1 so that the arrow^` iSd-is opposite line. N, the bar 55| is in the position'fornegative pitch control, in which position the highland |55 is engaged .by the valve |55. The body I2!` has ports |55, |56 connected by pipes |51 and |58 with one :outn et of a fluid pressure pump '|55 having three gears lei. Pipe |58^hasa relief valve |55; The right endof :cylinder |55 of valveunit |25 `is connected 'by Vpipe. |92 "withanother voutlet of the iiuid. pressure pump ,|55 connectedi also by pipe |54 with the left end of "the cylinder 23 Vof valve unit 25.? Pipe |52 has la relief valve Pipell is connected withjan increased-pitch lock unit. .lll .comprising a`.cylinder .iil'receiving a pistoni |72 connectedwitha barV H3 surrounded by spring |14 which4 urges the piston |12 toward the right.l The .-bar |13 has an in#A clined '.camsurface |15 for .engaging a pin or Y cam follower |16 provided at the lower end of the governorvalve 42;,

When propeller speed decreasesV below vthe value for which.- the. -g'overnoris4 set; valve ,52

moves in toward the propeller shaft anddown as `in'Fig. 1,1 thereby connectingpipes eiland 3l and permitting pressure iluid to ilow` from the pump 8l` throughthe cylinder'23V ofY valve 213 into the pipe 22 to the lower side of piston |F,xthereby causing it to move up andthe blade `to move counterclockwise in order to decrease the pitch. The load on the engine being Y decreased, the engine speed increases whereuponthe governor valve 42V moves Yup. If the propeller speed is above the governed speed,'the valve itil` moves above the kequilibrium position and the pump 81 is connected by pipes 5l', 55; 35,` the chamber Y33l of; valve 24 and pipe 2| with the upper side ofthepiston i6, whereupon the piston nmoves down in order to increase the pitch and to increase the load onY the engine whereby itsl speedis caused to. di-

minish. I

Valve 5|! limits thepressure available for pitch change by blowing-oit through discharge ports 58 and 59.,For pitch decreasing purposes, the pressure is limited to values represented by line A-B (Fig. 1c), said values increasing slightly with speed increase. For pitch increasing purposes, the pressures required in line at various speeds are indicated by line A,-C. VIn order to be sure of obtainingthe pressures'A-Q means are A-D, which exceed pressures A-C by amarginV which allows for pressure drop in the oil line. This automatic means comprises a piston provided by the lower end of valve rod 55 and the cylinder 53 which receives it and which is connected by pipe 66 with the pipe 35 which is in the pitch-increasing line either for governed positive pitch as has been explained, or for governed negative pitch as will be explained with reference to Fig. 3. Whenever valve 42 rises to connect pipe "i9 with pipe 36, the pressure in pipe 33 is communicated by pipe 50 to cylinder 53 to effect an increase in the force which resists downward movement of rod 55 under the action of oil pressure upon the piston 51. Therefore the blow-off pressures of valve 50 rise from values on line A-B to values on line A-D. When the speed error is relatively small, either port 43 or port i4 is slightly opened. The pressure drop at these ports is relatively high; and the pressure in pipe 49 is higher than in pipe 35 or in pipe 31. Valve unit 5|) blows 01T by opening relief ports 58 and 59; and valve 12 of unit 15 is held in by oil-pressure above valve 12. Pump S2 is connected with drain 19. When the speed errors are moderate, pump 81 alone can maintain the flow required for the pitch-charges.

When the speed error is relatively great either port t3 or port 44 will be opened a substantial amount, and the pressure in pipe 43 will fall to such value that piston 51 of unit 50 will block ports 53 and 59, valve 12 will move outwardly by centrifugal force and block drain 1S whereupon pump 82 will discharge through check valve 34 to the line 85-86-3I--45L Pump S2 will supply the additional oil flow needed to eiTect a rapid change of blade angle while the speed error is relatively great. As the speed error diminishes valve 42 closes, pressure in pipe il!) increases, valve 5B blows-off, valve 12 moves in, drain 19 opens, and pump 32 becomes disconnected. The foregoing applies to governed negative pitch as well as to governed positive pitch, as will be apparent from the description of Fig. 3 which is to follow. Other uses of pump 82 while changing from positive to negative pitch and vice versa and while going into feathering are to be described.

During the status of the system for positive governed pitch control, the switch-over unit 23,

the pitch control unit IZQ, the pitch-lock |13 and f the feathering valve 93 remain in the condition shown in Fig. 1. The accumulator IIs is connected with the pump 81, or with pumps 51 and 82, by pipes 86, 6I, cylinder 92 or" unit Sii, passage |53, open check valve iilfi, recess |152, passages IGI, IllEl and pipe HSC. The check valve IEM closes under the urge of spring 5&3 to maintain pressure of the duid in the accumulator that is obtained.

Fig. 2 illustrates the condition of the system after the cam bar |51 has been moved upwardly .in order to obtain the shift into negative pitch but before the shift has actually occurred. The upward movement of the bar I5! results in right movement of the valve |46 which blocks the drain |143 of pipe |32 and the drain |42 of pipe |51. Therefore, pressure fluid is delivered by pipe |64 to the left end of switch-over unit 2!! to cause it to move right in the position shown in Fig. 2. The blocking ofdrain pipe |51 causes pressure fiuid to enter the cylinder il'I of pitch-lock unit |10, causing the piston |12 to move left and the bar |13 to engage the pin |15 to lift the governor valve I ft2 to the position shown. The pressure uid circuit of the pumps 82 and 81 `is indicated by the arrows in Fig. 2. More specically, the circuit includes pipe 8 I, open check valve et, pipes 85, 86, BI, pressure control cylinder 5I, pipe 43, pipe 33, cylinder 23 of valve 23 and pipe 22 leading to the lower side of the piston I 5. Since pipe 36 is in this circuit, pipe Ei] conducts pressure fluid to the cylinder 53 of the pressure control valve 5t to urge the valve 51 up, thereby closing ports 58 and 59 and allowing centrifugal force to hold the valve 12 of pump control unit 13 in the upward position, thereby blocking the drain 19 of pump 82. Piston I6 moves up to cause the blade to be shifted from a position of positive pitch shown in Fig. 2 to a position of negative pitch shown in Fig. 3. During this movement, the cam |30 rotates counterclockwise from a position such as shown in Fig. 2 to a position such as shown in Fig. 3. During this movement, the valve |23 is engaged by the rise |3Ia, the land |32 and the rise I33a. The middle points of rises I3Ia and I33a determine, respectively, the lower limits of the ranges of positive governed pitch control and negative governed pitch control. That portion of the cam |30 between the middle points of the rises and including the land |32 is a surface of transition between positive and negative governed pitch status. Once the blade has started moving away from the positive governed pitch range, it must move all the way into the negative governed pitch range, and vice versa. There is no governing action while the blade is going through zero pitch.

By the time the blade has arrived in the position shown in Fig. 3 wherein governed negative pitch control is present the valve groove liti will be in a position for completely uncovering the port |412 so that the pipe |51 is connected with drain MI and the pitch-lock unit I1@ is restored by the spring |14 to normal position whereby the governer valve '42 returns to normal position for controlling negative pitch. The valve 2li has switched connection between the pipes 355 and 31 and the ends of the cylinder iii so that, when the governor valve 42 moves up, pipe 33 will be connected with the lower end of the cylinder I5 as indicated by arrow a, and when the governor valve moves down, the pipe 31 will be connected with the upper end of cyl inder I5 as indicated by arrow b in Fig. 3. The governor le will operate to govern the negative pitch just as it is operated to obtain governed positive pitch. The pressure control 5i) operates as before to give a higher pressure for increasing negative pitch then for decreasing negative pitch.

As in the case of increasing positive pitch, this is necessary because more force is required to increase negative pitch than to decrease negative pitch.

Fig. #l shows the condition of the system after the control cam |5| has been moved down into the positive-pitch control position but before the change to positive pitch has been made. Valve |23 remains in the negative pitch control position but valve |45 returns to the positive pitch control position under the action of spring I @5a and the pressure in cylinder |33. Valve land |48 blocks the connection between pipe E51 and drain iai. Therefore pressure uid flows from the pump IBI) to the cylinder 'Si of the lool; unit im, thereby causing the governor valve iii to be lifted so that its governing action will be withheld during the transition from negative pitch to positive pitch. This movement of valve iliii to the position shown in Fig. 4 causes pipe |32 to be connected with drain N53, thereby relieving the 'pressure at theileft of valve 24 of switch-over unit 2li', thereby allowing spring 35 to restore valve 24 to the position shown in Fig, i. Under these conditions, the upper end of the cylinder i is connected with the pumps 8:2 and 8l as shown by the arrows. The pressure line comprises the pipes 35, 86, 5l, 49, 36 and 2l. Since pipe 3B is in the line, pipe 5% conducts pressure fluid to the cylinder 53 of the pressure control 5t so that relatively high pressure is available for making a quick shift from negative to positive pitch. When this shift is made, the valve I23 is restored to the position shown in Fig. l, thereby connecting cylinder lll of the lock unit il@V with drain M2 whereupon the governor valve 42 is permitted to return toits governing status. Then positive pitch control becomes effective again in the manner explained with reference to Fig. 1.

The control of the lower limits ci governed positive and negative Y pitch control by the cam rises i310: and |33a,v respectively, will now be described. Referring to Fig. l, if during the governed positive pitch status, the land it of governor valve t2 were in position for opening the port to pipe 3l to cause counterclcckwise rotation of the cam 36 to such extent that the middle point of rise I3Ia engages the valve 22 oi unit iZil, this valve will have been moved left Vto a position which blocks the ilow of oil from pipe l5? through M5 and M2 thereby causing pressure oil from pump |50 to move the bar of unit il@ to the left to lift the valve so as to block the rlow of oil into pipe Si, whereupon counterclockwise movement of cam itil rThus the positive pitch is limited to a value determined by the engagement oi the middle point of rise ila with valve |23. Referring to 3, ii, duringrgoverned negative pitch status, the lands it of governor valve t2 were in position for opening the port to pipe 3l to cause clockwise rotation of the cam |30 to such extent that the middle point of rise 33@ engages the valve 23 or unit E2G, this valve will have been moved right to a position which blocks the ow of oil from pipe ii'! through either E55 or ifi, thereby causing pressure oil irom the pump it to move the bar H3 of unit Il@ to the left to lift the Vvalve i2 so as to block the flow of oil into pipe 3l whereupon counterclockwise movement et cam 93E! ceases. Thus the negative pitch limited to value determined by the engagement of the middle point of rise i330: with valve E23.

Fig. 5Y shows the control for ieathering but before feathering has actually taken place. The control for ieathering is effected by movement ci the parts H8, Hrt into the extreme right posi-Y When the blades'are about at H (Fig. 5), windmilling has decreased to the value such that the iiuid pressure from the pumps is insufficient to Y complete ieathering. Then pressure from the accumulator is'vinstantly available to complete the lieathering. As part H8 is moved into the position shown in Fig. 5 to obtain ieathering, lug ill strikes lug H6 and causes valve Ii to open.

Yshaft i8@ by the splines i355.

8. By means Vnot shown in Fig. 5, but which will lbe described later, valve |04 isr Vheld. open atleast until the blades have moved to position Il at which the windmilling has diminished to such extent that the use of accumulator pressure is required to Ycomplete feathering. While Yvalve is open, pressure oil from the accumulator flows through passages i963, It! and lill and into the annular space between the valve seat 9? and the land face Qta, thereby causing the valve t5 to move from the position shown in Fig. 5 toward that shown kin Fig. 5A, thereby moving valve portion Q from its seat 8l, thereby connecting the accumulator directly with the space at the left of land se. While pump pressure exceeds accumulator pressure, land 9&2 is located to the iei't or" the entrance to pipe 5i; but, when pump pressure falls below accumulator pressure, valve t5 moves to the position shown in Fig. 5A, and the accumulator supplies pressure to the pipe Si and to the upper end of cylinder i5, thereby causing the piston It to move down in order to move the blade il from the position il to the ruil feathered position shown in Fig. 6. Upon completion of iull-ieathering ilow oi. pressure fluid from the accumulator ceases, and the pressure diiierential on valve becomes so iar 'rw duced 'thatspringliil returns valve Q5 to the position shown in Fig. 1, where valve S8 is forced against its seat El and valve iet is closed. rFois retains the pressure-uuid in the accumulator until needed for unfeathering.

Full-feathering of the blades is effected when conditions are such that the engine should be non-operating and hence should not be rotatedv by the windmilling action oi the propeller. When conditions are such that the engine may be operated again, parts i i8 and i i3d are shifted to the positions shown in Figf in order that spring i8 will move the valve i2 down and in order momentarily to open the check valve its thereby permitting pressure iluid'to flow from the accumulator to the left side of land iii and thereby causing the valve to move to the position shown in Fig. 6. Then the accumulator is connected with the under side oi piston iii indicated by the arrows; and the pressure fluid stored therein iiows through the valve so, 'pipes Si, (i9, 3l, 22, to the lower end of the cylinder l5 to cause the piston it to move up to shift the blade H from full-feathered position into such position that the blade can be windmilled to start the engine whereupon governed positive pitch will be resumed. As pressure fluid from the accumulator isl discharged, the spring it?, becomes effective to return the valve to the position shown in Fig. l; and the status of the valve unit Si) returns to normal and charging oi the accumulator by the pumps is resumed;

rThe system of the present invention is part of a propeller hub assembly shown chiefly in Fig. 7. The engine shaft E85 supports conical V.vedges it! and. 982 between which ther is wedged a bular sleeve $83 splinedly connected with the rihe sleeve 83 clamped between the wedges by tightening a nut ia threaded on shaft ISB. Sleeve integral with the hub frame 85 having two or more tubular parts [8'5 extending radially relative o the axis of shaft 130. Each part itl) provides bearings lill for a blade, the root of which indicated at l88 (represented by the root i2 ci Fig. l) A nut E89 retains the bearings it? and a nut i953 retains theV propeller kroot its. InV alignment with each blade root itt, the frame |85 provides a boss |9| to which there is fixed a stationary sleeve |92 having helical splines |9211 cooperating with helical splines |93a of a sleeve |93 attached to a piston |94 within a cylinder |95. Sleeve |93 has helical splines |9519 cooperating with helical splines |951)` of cylinder |95 which is rotatably supported by a ball-bearing |98 carried by the boss |9|. The piston |915 corresponds to piston l and the cylinder |55 corresponds to cylinder |5 of Fig. 1. Sleeve |92 being stationary, the linear movements of the piston |96 are accompanied by rotary movements thereof due to the splined connections |93d and |92a. Due to splined connections iib and |95b, the linear and rotary movements ci the piston sleeve |53 effect rotation of the cylinder |95 and of the blade root IBB. The other blade or blades, not shown, each have a servomotor similar to that shown in Fig. 7. The blades are tied together by a gearing so that they rotate simultaneously and equally. For this purpose, each blade is provided with a gear segment |91 which meshes with a master gear |93 journalled in a ball bearing |98a supported by a frame |99 attached by screws |99a to the hub frame |85.

The sleeve |53 of frame |85 supports the plate 25| (Fig. 7) of a regulator unit 299. Plate 25| is located by a dowel Zilla (Fig. 19) in frame |55 and is clamped against frame |85 by a sleeve 252 threadedly connected at 252e with the sleeve |35. When the sleeve 292 is screwed tight, it forces the plate 20| against the surface i550. which is formed at right angles to the axis of the propeller hub. Screws 293 attach to the plate a housing 205 which supports a ring 255 which is journalled on a non-rotatable annular frame 255 intermediate annular frames 25'? and 293 which are all secured together and thus provide the fixed part of the regulator hous ing. In order to fix these parts against rotation,'there is secured to the part 251 a plate 255 having a tang 2H) which fits in a notch (not shown) provided by the engine frame. The part 295 provides a journal for a ring 2H xed within a tubular boss 2|2 provided by the regulator plate 25|. A' shaft seal 2|3 is located in the recess provided by the plate 20| and the ring 2l| and engages the sleeve 298 in order to prevent the leakage of oil from the annular chamber provided by the regulator unit. Likewise a seal '2id at the right `end of the unit, serves the same purpose.

The stationary annular members or sleeves 225, 29| and 253 support certain manually operated control devices. One of these devices is means for varying the governed speed of the propeller. It comprises a ring or internal gear 22S rotatably supported by the part 251 and rotated by a lever 22|. The gear 220 meshes with plurality of (preferably three) pinions 222 which operate shafts 223 journalled in the part 256. Each shaft 223 provides a screw 22e threaded through a grooved ring 225 whose groove 225 receives a shoe 221 located on a pin 228 attached to a carriage 229 guided by ways 23! provided by the governor which is attached to the plate 25|. The carriage 229 supports the fulcrum roller l' as is shown in Fig. 1. Movement of the lever 22|, for the purpose of changing the governed speed, is transmitted through the rotating shafts 223 and screws 224 to cause axial movement of the ring 225 in order to change the position of the fulcrum 41.

The stationary part 298 provides a gear 23| 10 which meshes with a plurality of smaller gears, one of which is shown at 232 in Fig. 'i'. The gear 232 drives the main pump 8l which is of the well known gear type and is secured within a recess gli provided in the plate 25| for this purpose. The pump outlet is connected with a passage Elo which leads to pipe line 55 which is embedded in the plate mi. In `fact practically all of the ducts shown in Fig. 1 are contained within the plate 29| except the few that are external thereto as shown in Fig. l0. The various ducts which are enclosed within the plate 20| are shown in 14 bear reference numerals correspondl ing to the parts shown in Fig. 1.

As shown in Fig. 9, the lock-out unit |19 (Fig. l) is secured to the frame of the governor 40. The pipe iii? which connects it with the pitch control valve i2@ is shown in Fig. 10. 'I'he pipes |55 and i652 which connect the pump |50 with the switch-over valve 293 and with pitch control valve |25 are not connected exactly as shown in Fig. l; but they are connected by the frame |2| of the valve |25 as shown in Fig. 10. The eX- ternal pipe 52 connects the pump control valve "Et with the pressure control valve 59.

As previously stated with reference to Fig. 1, the outlet of pump 5l is connected with pipe 96 which, as shown in Fig. 14, leads to a filter 235 represented by the dotted circle in. Fig. 14 and ,z actually shown in Fig. 13. The lter is screwed into an insert 235 forming a pad for receiving the pressure control valve 59. The outlet 23'! of the filter is connected with a duct 238 which is connected through duct 2350i with the cylinder 5| of regulator 55 and which is also connected with a duct marked iQ- 5| in Fig. 14 (since this duct performs the function of the pipes t9 and 5| in Fig. l). The construction amounts to placing a filter between pipes 86 and 5| in Fig. 1. Hole 5cc in pad 235 is a continuation of pipe 5c which is connected with pipe 2| which is connected with the pitch-increasing side of governor 4U.

Numeral 2st indicates a pad insert in the plate 2|l| for receiving the pump control valve lll (see Fig. l0). Pad 245 provides a hole 85a connected with pipe $35 which branches from duct 49-5L Since pipe l5 is connected through the nltel1 235 with duct #i2-6|, this amounts to connecting the pipe directly with the pipe 85 as shown in Fig. 1. rlhe hole @5c is connected with the check valve 54 shown diagrammatically in Fig. 1 and built into the valve unit lil. The pad 24|) provides the duct 85 which is connected with the duct tl connected with a hole Sie with which the outlet or the pump 82 (Fig. 1) is connected, when this pump is secured to the plate 29| The hele 85 leads to the cylinder ll of the valve 19 and is connected through the check valve Sil with the pipe 85.

Plate 2m provides a pad 2G15 for receiving the feather control valve unit (Fig. l0). Pad 245 provides a hole 25e making connection with duct #l5- 5| and a continuation thereof ltd-51a. The hole 2135 provides a connection between the pipe Si and the valve cylinder 9| shown in Fig. l. Fad 255 provides a recess which is connected by the pipe lice a port H92; and a passage 21| (Fig. '7) with the accumulator H9.

The plate 22| provides a pad 25e for receiving the governor fill. 1t has holes 350;, Sla and 45a connected respectively with the pipes 35, 31 and Ils-tia.

The plate 25| provides a pad 255 to which the switchover valve 29 is attached. The `pad passages 35?) and 31h connected respectively with ling; to a torque unit. A Mil: of pipe |190 becomes connected with pas- 11 pipes -36 and 31 for making connections with theY cylinder 23 of valve 2|! (Fig. 1). The connections between the cylinder 23 and pipes 2| and 22 include filters. For this purpose, the pad provides recesses 25S and 251 for receiving filsage 21| (Fig. '7) leading to the accumulator I9. The accumulator ils, as shown in Figs. rI and 8, comprises a cylinder 212 having an inlet 213 located in alignment with an annular groove 214 Vconnected with the passage 21|.

The groove 21@ isy located between seals 215. Cylinder 212 has, an inner end member 21% and an outer end member 211 into which a check valve 212 is threaded. Valve 218- resembles a tire Valve and serves to retain Vair under pressure forced into the cylinder 212 and causing a diaphragm piston Z to beforced toward the inner wall 215 as shown in -Figl 7. The cylinder 212 is retained by a snapV ring-28| received by a groove in a ring |2217 secured by the screws lega to the frame |85.

The parts |29 and |9919 provide a housing for a cam unit (Figs. 27 to 32) comprising parts 290 YandV 29i which are` assembled as shown in Figs. 29V and 30 in order to provide the cam lands |31, `|732 and |33 indicated in Fig. 1. These parts are made separate so that an adjustment can be made between the rise |3|a and the rise |330! in order to. adapt the mechanism for various engine and propeller blade combination. The outer member 29e is Vsecured to the gear |98 in various positions of angular adjustment by providing the -hub of the gear |28 with an external, circular row of semi-cylindrical notches 292 (Fig. 29) and the outer member 29@ with an internal, circular row of semi-cylindrical notches 293 of the same size. The annularspacing of these rows of notches is slightly diiferent. When the parts are adjusted l at the proper angular relation, a peg 2% is driven intofthose notches which are in radial alignment. In asimilarmanner the member 253i is attached -to the member 29d in various positions oi angularV adjustment. A peg 295 is received by that notch 29S of part 29E which is in radial alignmentfwithfthe notch 291 of part 299 when the parts 29H and 25| have been relatively adjusted to the desired angular relation. In order to provide a control for the feathering valve Sil as will lbe explained later, the cam member 29|) is pro- 'vided with a recess or notch which defines a land 298 joined by a rise 2%? with land 133.7.' which is flush with land |33.

The valve |23 of Fig. 1, is not directly cn- -gaged bythe cam lands itl, 32 and E33 as shown in Fig. 1 but indirectly by a push rod 360 (Fig. 19). The push rod 32|) is supported by the frame |85 and is urged toward the left by a spring 30| which forces a cam follower 3&32 attached to the rod 300 against the cam. As shown in side View in Fig. 25, follower 322 provides an arcuate surface 303 tting the inner surface of the part |99, thereby preventing turning of the follower. The tang30li of the follower is the part which engages the cam 290. As the blade arr/8,103'

12 root |88 (Fig. 7)'is rotated, the cam members 29@ and 29| are caused to rotate in order to control the valve |23 in the manner which has been explained with reference to Fig. l.

The valve |46 of the pitch control valve unit i2@ is maintained by a spring ilia in contact with a plate 3m which is manually shifted axially of the engine shaft by means which corresponds to the function of the part 15| of Fig. 1. The means for shifting the plate 319 comprises a ring 3H rotatably supported by the part 281 and having a manually operated lever LN2 and carrying three equally spaced cams 3i3 shaped as shown in Fig. 26. Each cam Slis controls the movements of the rod or cam follower Sill supported by the parts 206 and 221 and connected with the plate 3H). Each rod Sil@ is urged toward the cam 3|?, by a spring Sie.

As shown in Fig. 20, the piston of the feather valve unit 90 comprises parts 95u and 35h. The cylinder 9| is received by recess 22'!" in pad 245 of Fig. 14. The passage 2de in this pad is connected with the interior of the cylinder 9| by holes 9 la which are enclosed by a frame 320 secured to the pad 225 and sealed by ring Sie. The accumulator is connected with the pump line 3S-el by the passages @Ea and passage |26 through which the valve rod il@ extends, the recess around opened check valve it, passages i612, Nil and m0, and cross passage S35i leading to groove 93 which is connected by duct i with the accumulator. Flew of oil under pressure from the accumulator is prevented by the closing of the check Valve Hit when the pressure in the accumulator exceeds the pump pressure. The valve |94 is opened by ccunterclockwise movement cf the lever i12 which is biased in a clockwise direction by a leaf spring 15 corresponding to spring iiEi in Fig. 1. The lug ii'i of Fig. 1 which operates upon the lug iis of lever |12 is carried by a part 322i corresponding to the part H8 of Fig. 1. The part 22| is supported by part 322; and both parts 32E, 322 are guided for horizontal movement (Fig. 2G) by ways 323 and 324 (Fig. 21) having iia-nges 525 and 326, respectively, attached by screws E221 and 328, respectively, to the frame 329. The ways have ears 329 and 330, respectively, carrying a cross pin 33E which serves as a stop for limiting .clockwise movement of lever H2 as shown in Figs. 19 and 24. The part 32| has notches 332 for receiving a pin nxed to the part 322 as indicated in Figs. 21 and 22. A spring 33d located between the parts 532i and 322 (Fig. 20) urges them apart; and the separation limited by the engagement of pins 332 with the right ends of the notches 332 as shown in Fig. Y

22. The part 32| therefore moves with the part 322 unless prevented by doing so by means to be described. The part 32| has a tubular extension 335 which receives a rod 331i retained by a cot-- ter pin 331 passing through it. The lower end of the rod carries a shoe 333 received by the groove 226 in the ring 225 which is manually adjusted as described for the purpose of shifting the fulcrum members al1. Since this control ring 225 concurrently adjusts the fulcrurn (i1 and by the part 32,2 which moves the lug H1, the member ||8a of Fig. 1 has been used to represent the common controlling element for both of these members; but, actually, each of these members has its own connection by a shoe with the control ring 225.

When it is desiredto stop the engine while in flight full feathering of the blades is required abnormal pressure.

vin order to prevent operation of the engine by the wind-milling of its propeller. As stated with respect to Fig. 5, the fulcrum 41 of the governor 40 and the lug H1 controlling feathering valve 90 are moved into feathering control position. The engine is rendered non-operative. During a portion of movements of the blades from the position shown in Fig. to that shown in Fig. 6, the engine is wind-milled at high speed and the pressure of the torque unit operating pumps is substantially higher than normal. It is advantageous to keep the check valve |04 open during the high wind-milling period in order that the accumulator may be charged at the Extra pressure in the accumulator is needed to complete feathering after wind-milling and pump pressure has substantially diminished, because the pressure required to increase blade pitch to full feather is higher than normal especially when the air speed is high. The check valve |04 is positively held open at least until the time that pump pressure falls below accumulator pressure, so that the accumulator pressure is instantly available to effect full-feathering. Then the check valve |04 closes in order to retain the remaining accumulator pressure required to move the blades out of feathering. This control of check valve |04 will now be explained With reference to Figs. 19-24.

During the normal range of positive governed pitch the cam 290 holds a cam follower 340 in the position shown in Fig. 19. The follower 340 is attached to a rod 34| (guided by frame |85) which holds a plunger piston 342 in such position as to cause a spring 343 to urge a plunger cylinder 344 against a lug or tail 345 extending from the way 323 shown in Fig. 19. When the control ring 225 is moved into the position to demand feathering whereby` the fulcrum 41 is located as shown in Fig. 5, the shoe 338 is also moved toward the left from the position shown in Fig. 19. During a portion of this movement the parts 32| and 322 move together and the lug ||1 moves against the lever ||2 to cause it to move counterclockwise as the lug rides along the lug I6 into the position shown in Fig. 20. When lever I2 arrives at the position shown in Fig. 20, a lug or tail 346 depending from the part 23| strikes the plunger 344, and movement of the part 32| is arrested since the spring 343 is stiffer than the spring 334. While the lever ||2 is held in the position shown in Fig. 20, the ball check Valve |04 is held open; and it will remain open although the part 322 is moved further to the left by the control ring 225. Fig. 23 shows part 32| in the same position as shown in Fig. 20, whereas part 322 has been moved further toward the left thereby compressing the spring 3,34 beyond its normal state of compression. This means that, although the control ring 225 has been manually actuated so as to obtain full feathering, the ball check valve remains in the position shown in Fig. while the cam 299 is approaching a position corresponding to which the blade angle relative to full feathered position is relatively 10W( (for example about 30). Before that angle is reached, `the wind-milling action has Vdecreased to such extent that pump pressure is below accumulator pressure. The check valve |04being still open, valve 95 is caused to move by accumulator pressure to the position shown in Fig. 24 and the accumulator is connected with the servo-unit I5 to complete the feathering. When the cam `290 has arrived at a position corresponding to a blade angle of 30 from full-feathering, the cam land 298 has moved into alignment with the follower 340. The rod 34| and plunger 344 move left to permit part 32| to move by the action of spring 334 into the positions shown in Fig. 24, and lever ||2 returns to normal position so as not to obstruct movement of the check valve |04 to closed position when full-feathering has been completed. When full-feathering has been effected, the flow through ports 9|a ceases and spring |03 restores the valve member to normal condition preparatory to return from full-feathering to positive governed pitch as explained with reference to Fig. 6. The right movement of part 32| from the position shown in Fig. 24 to that shown in Fig. 19, effects, through lug ||1 striking lug H5 of lever I |2, a momentary opening of check valve |94 which is suflicient to cause valve 95 to move by accumulator pressure to the position shown in Fig. 6; and the accumulator is connected with the torque-unit for the unfeathering function.

The disclosure of the switch-over valve unit in Figs. 10 through 13 is substantially the same as in Fig. 1 with the exception that there is a liner 23a within the cylinder block 23. Fig. l1 shows that there is a filter 251a between the valve 20 and the outlet 259 to duct 22. Fig. 13 shows that there is a filter 25641 between the valve 20 and the duct 2|.

Fig. l0 shows that the pump 82 is mounted upon plate 20| about diametrically opposite pump y81. Pump 82 is mounted in the same manner as the pump 01 and is located in a recess 821, Figs. 14 and 16. It is driven by a gear 348 which meshes a gear 23|.

Gear 23| drives gear v"349 attached to one of the three pump shafts |6|a of pump |60. The shafts |5|a are attached to the meshing pump gears ISI. 'Ihe pump inlets 350 and 35| are shown in Figs. l0 and 14 and the outlets leading respectively to pipes |51 and |62 are indicated at |51a and |620, in Fig. 18 Which shows the checlfL valves |59 and |63 as part of the pump structure. The springs |590'I and |6311, which respectively urge the check valves toward their seats, are retained by a bearing 352 secured by screw 353 to a plug 354 forced into the bore for the middle shaft |6Ia.

Fig. 10 shows the use of one or more counter- `weights 390 secured by screws 36| to plate 20| for the purpose of obtaining a balance of the rotating structure.

The accumulator body 212 is used as a wrench for tightening and loosening the nut mtu, Fig. 7. For this purpose the body 212 is provided with notches 212D for receiving lugs extending from the nut |3011. The body 212 is provided with serrations 2120, which extend exterior to the hub assembly and to which a wrench may be applied in order to force the cones |8| against the pro-` peller hub |83 or to retract the same. When the accumulator body 212 has been tightened, it is prevented fromv turning by placing over the serrations a disc |990 having internal serrations which match the serrations or splines 212@ of the body 212. The disc |99c` has tangs which are received by notches |999 in the ring |9912. The disc |99c is retained by a snap ring |99d. The ring |9912 forms a cover for the chamber |99 and is `secured by the screws |99a which secure both the cover |99 and the ring |9912 to the hub |95.

Rsum

In making the change from the positive to the .pressure control valve 58.

In shifting from the positive pitch rangev during the shift'is the one which, duringY positive pitch control, is the pitch-increasing port. ThatV port becomes, due to the reversal kof ccnnections between the governor and the cylinder, the positive-pitch-decreasing port and then the negative pitch increasing port. Conversely, during the shift from the negative pitch range to the positive pitch range,rthat. same port is held open because, due to reverse of connections again, it becomes the negative pitch-decreasing port and the positive pitch-increasing port. The shift from one range to the other is always completed before the governor valve `is releasedfor normal operation.

'Ehe switch-over valve 2G Ywhich controls the reversal of connections between the governor ports and the torque unit cylinder-and the governor valve retainer or lock-out Hij are controlled by the unit H2B which has a manually operated valve which effects concurrently the reversal of connections by the valve -2'8 and the functioning ofthe lock-out lill, and which has a valve i23 controlled automatically by cam ist in response to shift of the blades fromr one pitch range to the other for disabling the lock-out. For this purposethe cam I3@ provides a lou7 land 53| and a high land 533. Instead of a continuous rise between the lands i3i and 33, an intermediate land i252 and two short rises iiia and liid are provided. The land H32 merely spaces the rises i350, and 3311 which so control the valve |23 as to place yminimum limits on positive and negativepitch, respectively. Therefore the unit l2@ functions to effect .the shift between positive and negative pitch and tov pr vide the minimum limits. of positive and negative pitch control.

The pump 8l provides the oil ow required for pitch-change to correct'small speed errors Oil iiow under pressure from thepump S2 isv demanded only when necessary toinaintain Ythe iiow rate required to initiate the correction of a relatively large speed error or to. effect a rapid change from positive to-.negative pitch, or vice versa, o-r to effect feathering up to the instant that pump pressure falls below acciunulator pressure. Normally, pump 8'! is idle most of the time,V and very little power is required for its idle operation. Valve 'Ill which controls the opening and closing of drain 19 of pump 8l operates as an hydraulic Vrelay under control by the So longA as the oil line pressure tends to exceed the pressure limits set by the valve 56 atvarious speeds, the valve 5B blows-off and causes valve 'Hl to connect pump 8l with drain 1S. When oil line pressure falls below the limits set by valve 5ta at various speeds, the valve 5e ceases to blow-off and valve Y'lil effects the closing of the drain `'ll'of pump 8l. Valve 5d senses the difference between required pressure and pressure actually suppliedvto the line by pump 8?, and effects the flow of oil from pump 82 into the pressure line when the actual pressure falls vbelow therequired pressureanclV causes the pump .82 'tov become idle when actual pressure equals or exceeds required pressure.

In order to ,minimize heating of the oil, valve 5i! is set by a properly calibrated spring 55 to blow-ofi at the pressures required for pitchdecrease at various speeds. Only when pitchincreasing is demanded, the blow-olf pressures are increased automatically. The blow-0E pressure increase is eiectedin response to pressure in lineV 36 which is communicated through pipe St to the cylinder a3 of vvalve eil. The pump 82 is able to provide the increase andtc effect a flow rate for pitch-increase to correct a moderate overspeed wit-hout the aid of pump S1.

Y As stated before, when feathering is demanded both pumps are discharging into the line. The engine being idle, windmilling of the propeller takes place during the shift into full-feathering. Windmilling causes the pumps to operate at speed and to produce oil pressure in excess of normal. Naturally the check valve its of unit et would open to admit oil at the abnormal pressure to the accumulator; and it would close again when, as the blades approach full-feathering position, the windmilling diminishes and pump pressure falls below accumulator pressure. In. order that the accumulator might discharge to complete the feathering operation after pump pressure falls, some means would be required to open the check valve its in order to effect a right movement of valve and aneifectivedischarge of the accumulator. The present invention provides means for open-ing the check-valve itil in 'advance of feathering by the operation of the feathering control member and meansfor hold- Y ing the check-valve open at least until windmilling had diminished tolsuchextent that pump pressure is less than accumulator pressure. VDuring the period when pump pressure is higher than normal, the accumulator is being charged at this higher pressure so that it is all the more effective to complete the feathering` and still has a reserve of pressure for' unfeathering. The instant the pump pressure falls below accumulator pressure, check-valve ls being then held open, the valve 94 of unit Sil immediately moves right to allow the accumulator to discharge freely to complete Vthe feathering operation. Before feathering is completed (30 before in the disclosed apparatus), the mechanical means which had held the check-valve its. open is automatically disabled. Therefore, the. check-valve les -Will be returned by spring H33 to its seat in advance of return of valve-94 to its seat 8l which happens when feathering is. completed and discharge of the accumulator ceases. When the feather control member is moved to unfeathering position, the check-valve lila, is momentarily opened; and, in response thereto, valve 9G auto-- matically moves right to permit the discharge of the ac-oumulator'to effect movement of the blades from full feathering at least to such angle that windmilling can take place andthe pumps become eiiective again to restorethevblades tov the positive control range.

VWhile the embodiment of the present invention as herein disclosed, 'constitute a preferred form, it is to beunderstood that other forms might be adopted, all coming Within the scope ofY the claims which follow.

What is claimedA is.l as`A follows:

l. Propeller pitch control. apparatus, the combinationV with an, bladehaving a :rotatably supportediroot, of an hydraulically operated torque unit forrotatingthe blade including a. cylinder and a piston movable therein, an oil pressure source, a governor having an inlet connected with said source and outlet ports connected respectively with the ends of the cylinder and having a speed responsive valve for controlling the flow of pressure fluid from the inlet to either of said outlet ports, a switch-over valve included in the connections between the governor and the cylinder and providing in one position for control of oil pressure to the torque unit in the positive-pitch range and, in the other position which reverses the connections between the governor and the cylinder, for control of oil pressure to the torque unit in the negative-pitch range, means for moving the governor valve in position for connecting the pitch-increasing governor port with the pressure source and for retaining the valve in said position, means for effecting movement of the switch-over valve and the operation of the governor valve retainer to obtain a shift from one pitch range to the other, and means for rendering the retaining means non-operative when the shift from one range to the other has been accomplished.

2. Propeller pitch control apparatus, the combination with a blade having a rotatably supported root, of an hydraulically operated torque unit for rotating the blade including a cylinder and a piston movable therein, an oil pressure source, a governor having .an inlet connected with said source and outlet ports connected respectively with the ends of the cylinder and having a speed responsive valve for controlling the ow of pressure-fluid from the inlet to either of said outlet ports, a switch-over valve included in the connections between the governor and the cylinder and providing in one position for control of the torque unit in the positive-pitch range and, in the other position which reverses the connections between the governor and the cylinder, for control of the torque unit in the negative-pitch range, a device for moving the governor valve from a governing position controlling the pitchincreasing and pitch-decreasing ports of the governor into a position connecting only the pitch-increasing port with the pressure source, a controller having 4means for selecting the positive or the negative-range of control and operable manually for effecting a shift of the switch-over valve and the functioning of the governor-valvemoving device when a shift of the blades from one range into the other is required, said controller having means for rendering said device inoperative operating automatically in response to the shift of the blades from one range into the other.

3. Propeller pitch control apparatus, the combination with a blade having a rotatably supported root, of an hydraulically operated torque unit for rotating the blade including a cylinder and a piston movable therein, an oil pressure source, a governor having an inlet connected with said source and outlet ports connected respectively with the ends of the cylinder and having a speed responsive valve for controlling the flow of pressure fluid from the inlet to either of said outlet ports, a switch-over valve included in the connections between the governor and the cylinder and providingin one position for control of the blade pitch in the positive-pitch range and, in the other position which reverses the connections between the governor and the cylinder, for control of the blade pitch in the negativepitch range, a device for moving the governor valve from a governing position controlling the 18 pitch-increasing and pitch-decreasing ports of the governor into a position connecting only the pitch-increasing port with the pressure source, a

controller having a cam follower and means for selecting the positive or the negative range of control and operable manually for effecting a shift of the switch-over valve and the functioning of the governor-valve-moving device when a shift of the blades from one range into the other is required, said controller having means controlled by the cam-follower for timing the functioning of the governor-valve moving device, and a cam operated by the torque unit for actuating the cam-follower and having a contour such that said device is rendered inoperative automatically `in response to the shift of the blades from one range into the other. said cam having a contour such that said device becomes effective to move the governor valve into position for blocking the pitch-decreasing port of the governor when predetermined limits for positive or for negative tric with the hub tubular part for correlating the turning movement of said blades, a control cam unit supported and driven by said gear, a regulator assembly comprising an annular housing surrounding said hub tubular part, said housing including a non-rotating tubular wall surrounding the said tubular part of the hub and other wall members rotatively connected with the hub, said other wall members including a plate, said housing providing an oil reservoir, controlling devices supported by the plate and including a.

governor operative to control the torque units either in the positive or in the negative range of pitch control, means for controlling blade shift from one range into the other and having a manually operable control member for eiecting the shift from one range to the other and the non-functioning of governor during the shift and having an automatically operated control member for restoring the operation of the governor after the shift has been completed, a member operatedby the cam unit for operating the governor restoring control member, and manually operable means for adjusting the governor.

5. Propeller pitch control apparatus, thecombination of a hub having a tubular part adapted to be drivingly supported and having a plurality of radially disposed blade sockets, propeller blades journalled in the sockets for pitch shifting movement, fluid-pressure operated torque units Within the sockets for rotating each of the respective blades, means including a gear concentric with the hub tubular part for correlating the turning movement of said blades, a, control cam unit supported and driven by said gear, a regulator assembly comprising an annular housing surrounding said hub tubular part, said housing including a non-rotating tubular wall surrounding the hub tubular part, and other wall members rotatively connected with the hub, said other wall members including a plate, said housing providing an oil reservoir, fluid-pressure supply means supported by the plate, supply means actuating mechanism actuated by rotation of housing, an accumulator supported by the hub and charged by the pres- 

